Publié 08/07/2021
How HVAC operates against COVID-19?


The above studies establish how COVID-19’s airborne potential goes past the immediate surroundings of infected people. They also establish how concentrations are able to be diluted when ventilation is increased. During the 2003 SARS pandemic, investigators proposed the theory that increased exchange of air might have minimized spread of the disease. However, they didn’t have enough data to support ventilation rate minimums. One investigator cited ventilation as being a key player in the way COVID-19’s spread will inevitably be contained.

While window openings can minimize risks, there are not enough studies relevant to this topic in order to confirm this.

Distribution of Air

Field evaluations performed by the authors involving FCUs mounted on walls identified situations involving air supplies blowing right on occupants. This could potentially transmit the virus from individuals who are infected to others around them. Our assessment of various airflow patterns (that were stated in the restaurant outbreak’s study) indicates that this may have been significant. Air blown right on surfaces may re-suspend aerosols that contain the virus once settled. Distribution of air can establish if infectious droplets either concentrate locally or disperse. Relatively speaking, pressurization can either spread or contain contamination. There is a lack of data out there pertaining to patterns of airflow and their effect on transmission of COVID-19.


Surface sampling within HVAC systems recirculating inside of a hospital offers an indication of a filter’s efficiency, based on a recent report. The virus collected by the supply’s air damper, pre-filter, and final filter makes way for virus comparisons within mixed air – not just before pre-filters were used, but after as well (MERV 10). It also compared final filter discharge (MERV 15). SARS-CoV-2 gathered on surfaces was minimized by about 70% once they went through pre-filters. However, final filters didn’t decrease them any further.

An influenza spread modeling study revealed that air filters with higher efficiency could lower the risk of flu infection. While SARS-CoV-2 response measures currently include filter installation (ones with high MERV ratings, specifically), no studies exist to establish if filter ratings make a difference, as far as disease transmission is concerned.

With appropriate positioning and design, HEPA filters inside an area can minimize exposure to COVID-19 directly. It does this by capturing air within proximity to patients that are infected, or by eliminating airborne viruses that are close to vulnerable individuals. With that said, designers must be mindful that a discharge of air could blow the virus in-between occupants, re-suspending settled viruses lingering on surfaces.

Disinfection of Air

UV (ultraviolet) light systems to accommodate infection control may be either in the duct (HVAC system) or in a space (an upper room). Such systems are sometimes utilized in hospitals for the sake of controlling infectious agents that are airborne. However, they are seldom used in the average non-healthcare facility.

One study revealed that upper room ultraviolet had the ability to prevent measles, chickenpox, and mumps from spreading. However, it may not be very effective in protecting vulnerable individuals from other pathogens. A lack of research was found relative to UV use, as far as controlling COVID-19 is concerned.

Control of Humidity

Coronaviruses are able to survive even under the driest conditions. Occupants are susceptible to potential respiratory infections at lower RH (relative humidity). As a way of controlling the flu, humidification has been recommended. Contrasting the original cases of COVID-19 by country or region suggests that rates of infection may be higher in places with high humidity. With that said, COVID-19 has spread during the pandemic’s initial stages in areas that were humid.

Continuous high COVID-19 rates in the USA this past summer suggest humidity isn’t a key factor. In fact, the NAS (National Academy of Sciences) stated that humidity differences only explain small fractions of COVID-19 variations, as far as transmission rates are concerned.


COVID-19 has been discovered in air, toilet surfaces, sewage, urine, and feces in restrooms. Droplets containing viruses that are released from restrooms are probable, however, no trackable results were evident.

Mechanical Hygiene

COVID-19 lingering on surfaces within HVAC systems were recently studied – particularly in hospitals where air was recirculated in COVID-19 wards. SARS-CoV-2 was found on pre-filters that received mixed air, air damper supplies that were installed after final filters, and final filter surfaces that received air after pre-filtration. Another study revealed that an exhaust outlet’s hospital surfaces in Singapore received positive test results.

Table des matières

Publié 08/07/2021
How HVAC operates against COVID-19?

Table des matières